This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The long term goal of this collaboration is to determine the structures of F. tularensis surface molecules useful as protective antigens for vaccine production. Towards these ends we are characterizing the O-antigen portioni of the F. tularensis lipopolysaccharide. The structure of this O-antigen is known from nuclear spectroscopic evidence based on the bulk properties of the polysaccharide. In addition, the O-antigen composition consistent with this structure was reported based on matrix assisted laser desorption/ionization of the permethylated molecule. In initial studies, we are producing detailed mass profiles on O-antigen isolated from virulent and avirulent F. tularensis strains. We will characterize these structures in detail using tandem mass spectrometric methods developed at the Mass Spectrometry Resource.